Blast Furnace Tap Hole and Tapping of the Furnace The operation of a blast furnace is a continuous process. The blast furnace continues to produce liquid iron (hot metal) and slag as long as it is in operation. The hot metal and slag accumulate in the hearth of the furnace, but since there is a limit to the amount that can be accumulated before it interferes with the furnace operation, hot metal and slag must be removed from the furnace at regular intervals. The tap hole also known as iron notch, is used for tapping the hot metal from the furnace. It is located slightly above the floor of the hearth. Regardless of the specific tap hole configuration or operating philosophy, due to the addition of dynamic (often periodic) and more intense process conditions (exposure to higher temperatures leading to accelerated corrosion, greater turbulence, and elevated rates of mass and heat transfer), and higher concurrent thermo-mechanical forces (from thermal or flow shear stresses), the performance and longevity of the blast furnace is intimately linked to the performance of the tap hole. Hence tap hole is very critical to the blast furnace. It is the heart and the lifeline of the blast furnace since without a tap hole a blast furnace cannot exist. The criticality and relevance of tap hole continues even in the modern automated blast furnaces. Tap hole is an essential part of a blast furnace. Large furnaces usually have 2 to 4 tap holes and the drainage of hot metal and slag is practically continuous by periodically drilling and plugging the tap holes with one of the tap holes is always open and two alternate tapings usually overlap for some period of time. Medium or small sized blast furnaces have normally one...

Blast Furnace Tap Hole Mass Blast furnace tap hole mass is a prepared ready to use refractory product, made of a bond of aggregates, additives, and plasticizers. It is used to close the tap hole of a blast furnace after tapping so that no material can leak out, and to keep it plugged until the tap hole is opened for next tapping. It is applied to ensure periodical and stable tapping from the blast furnace and also to protect the inner surface of tap hole bricks. Its functions are (i) to enable smooth operation of the tap hole, (ii) to maintain constant tap hole length, (iii) to control the liquid flow out of the blast furnace, and (iv) to ensure separation of hot metal and slag. Blast furnace tap hole mass is normally developed and designed to suit the operating parameters of the blast furnace and to maintain stable tapping time and tap hole depth even under severe operational conditions with high productivity coefficients (ton/cu m/day) or high hot metal temperatures. Requirements of blast furnace tap hole mass Typical requirements from the blast furnace tap hole mass include the following. It should be soft and plastic (workable) enough to inject when pushed by mud gun, but ‘hard’ enough to effectively displace tapping liquid and to deliver a substantial quantity of tap hole mass only to plug to the required depth in the tapping channel. It should be curing to the required strength (often described as sinterability) and without shrinkage to ensure a tight seal within the tap hole (not prematurely in the mud gun), in the required mud gun dwell time and plug to next tap time. It should effect safe tap hole closure (i.e., without subsequently self opening) and without tap hole and...